Veeref From , joined Dec 1969, posts, RR:
Reply 2, posted (9 years 10 months 4 days 20 hours ago) and read 2044 times:
It is possible. Your best chance is sitting towards the very back of an airplane that has wing mounted engines. Longer models such as A321 or 773 are best.
The more saturated the outside air the more pronounced the contrail and in some cases you will get a visible contrail almost immediately behind the engine exhaust. In really humid air you may actually get aerodynamic contrails as well.
Only other time I've seen it was in holding patterns at high altitudes. As you circle around you can see you contrail from the opposite direction. if you make more than one circuit and the winds aloft are light, you might even get the chance to fly back through them!